1. Field of the Invention
This invention pertains to hydraulic valves in general and more particularly to the elimination of any pressure surges that may occur in hydraulic lines in order to gradually provide flow through the valve.
2. General Background
The use of hydraulic valves to regulate pressure or fluid flow is well known in the art. Such valves are needed for the operation of hydro-mechanical equipment and the like which are used in a variety of industries. However, a problem associated with the use of such equipment concerns the high pressure line surges that are caused by the opening and closing of valves or other control devices. Such opening and closing can cause instantaneous reactions of the hydraulic equipment which is not always desirable. Also, such surges, if too great, can damage the motors, cylinders, or piping of such equipment, another undesirable feature.
U.S. Pat. No. 3,739,807 to Landrus et al. discloses a hydraulic valve that is used to regulate pressure in automatic transmissions in order to prevent any abrupt engagement thereof. As shown therein, fluid under pressure enters the valve via line 16 and flows into chamber 26. Such fluid eventually causes valve element 38 to move to the right while compressing spring 56. This fluid also passes through orifice 50 and opening 65 to eventually cause plug element 66 to also move to the right against spring 72. When plug 66 abuts stop 76, the equal pressure on both ends of valve element 38, along with the force of spring 56, causes this valve element 38 to return or snap back to its original position thereby concluding the regulation of the applied pressure or trim cycle.
U.S. Pat. No. 4,030,522 to Heiser is an example of a hydraulic valve used to control the amount of pressure fluid flowing therethrough. In this case, a variable throttle 28 is inserted between a pressure fluid inlet passage 23 and pressure fluid outlet passages 26 and 27 in order to create a pressure difference between the two. This pressure difference is generally maintained by inserting a spring biased valve 43 between the inlet passage 23 and adjacent by-pass passage 25.
U.S. Pat. No. 2,476,720 to Gardiner is an example of another flow regulating valve which utilizes an adjustable throttle 54 for consistently driving machine tools regardless of the load thereon. In this version, a fluid is pumped via line 38 into inlet port 40 which is in communication with throttle 54 via passages 63, 71, 74, and 78. Throttle 54 is, in turn, in fluid communication with spring biased blocking valve 56 which blocks outlet passage 104. When sufficient fluid pressure builds-up in front of blocking valve 56 (as controlled via throttle 54 and compensating valve 52), such fluid is gradually released into outlet passage 104.
U.S. Pat. No. 2,164,669 to Thomas discloses a pressure relief valve that is used in power transmission systems. This valve incorporates a piston 42 that is exposed to fluid under pressure via conduit 32. Normally, piston 42 is in the closed position, but at some pressure value, piston 42 is moved to the right against the bias of spring 44. Piston 42 then remains in this open position until sufficient pressure is created behind piston 44 via by-pass 48 to assist spring 44 in closing piston. This valve is configured such that the opening pressure of piston 44 can be changed or adjusted without affecting its closing pressure. Likewise, the closing pressure of piston 44 can be changed or adjusted without affecting its opening pressure.
U.S. Pat. No. 4,682,531 to Mayer discloses a control valve that regulates the rate of fluid flow. This valve limits fluid flow to a hydraulic motor during start-up so as not to induce excessive loads thereon. It consists of a spring biased poppet 50 that is located intermediate fluid inlet 32 and fluid outlet 34. This poppet 50 is normally biased closed, but upon the application of pressure via inlet 32, poppet 50 is moved from its seat thereby allowing some of this fluid to pass via channel 80 and flow toward outlet 34.
U.S. Pat. No. 4,051,864 to Iwatsuki discloses a flow regulator for use in controlling fluid flow during the operation of such devices as fork truck lift mechanisms. This regulator dampens flow rate in order to maintain a consistent flow notwithstanding changes in load conditions. A dashpot is utilized to dampen such flow.
U.S. Pat. No. 3,086,551 to Gordon discloses a hydraulic relief valve which may be used to prevent hydraulic fluid pressure from exceeding a predetermined value. It operates by inserting a valve body 24 intermediate the inlet 14 and exit 16 fluid openings. This valve body 24 is normally biased closed via the hydraulic pressure in cylinder 44 and the bias of spring 68. However, when the pressure in inlet 14 is sufficient enough to overcome such bias, valve body 24 becomes unseated thereby permitting fluid flow to outlet 16.
As can be seen, there are a variety of different methods of controlling hydraulic pressures. All of these devices incorporate a labyrinth or maze of internal passageways which contain many moving parts. Their construction and assembly is thus time-consuming and expensive and they also require a high degree of maintenance to insure proper operation. It is thus an object of this invention to provide a flow control valve that is relatively inexpensive to construct and requires few moving parts.
Another object of this invention is to provide a new design for a valve that controls the initial surge pressure occurring in hydraulic lines.
A further object of this invention is to provide such control so as to either gradually provide flow through the valve or gradually provide no flow through the valve in the reverse flow situation.
Yet another object of this invention is to employ a spring biased plunger in conjunction with controlled fluid dampening to effect such pressure regulation.
Still another object of this invention is to devise a control valve for use on cranes and the like which will aid the operation or movement of its crane, boom and winch.
Another object of this invention is to provide a valve that can be used in pairs due to the movement of the crane's components in opposite directions.
Yet another object of this invention is to prevent erratic movement of the hydro-mechanical equipment to which the invention is attached.